1. Field of the Invention
The invention relates to a swing arm for moveably fitting wheels onto a support element, especially for the suspension of single wheels in passenger cars, thus fitting the wheels to the body of the axle.
2. Description of Related Art
Swing arms are widely known. They were normally produced by using the hollow-shell construction method, according to which they were welded together from at least two metal sheets. Due to the welding seams, the hollow-shell construction method required a comparatively heavy weight of material. Furthermore, it was not possible to produce cross-sections that could optimally withstand the stress. These familiar swing arms required high production costs. This resulted in an undesirably heavy weight of such parts, especially if an increased load capacity was required. Ultimately, the welding seams were often the cause of rejects. A certain structural space was necessary due to the required load.
Therefore, it is the object of the invention to create a simpler and lighter swing arm.
The problem is solved, according to the invention, by a swing arm, having at least two hollow arm parts, hollow moulded, using the internal high pressure moulding method (IHM method) optionally with variable cross-sections. At least one of the arm parts has at least one connecting projection which is inserted into and fixed in the end section of the other arm. The exterior diameter of the projections corresponds to the interior cross-section of the other arm part, so that the connecting parts can be placed thereon.
It is advantageous if the arm parts are made, at least partially, of cold-deformable metal, metal alloy or plastic that can preferably be strain-hardened, and if they have a fibre flow that runs parallel to the outer contours of the arm parts.
The hollow moulded parts can, therefore, be made of a single material, for example, steel or a light-metal alloy. Depending on the realm of application, it is also possible to deform laminated material, as well as plastic-coated or coated pipes.
Depending on requirements, it is also possible to use variable materials for the different parts of the swing arm, according to the invention. When taking the swing arm apart in order to recyle the material, the parts can easily be separated again from one another.
It is advantageous if the swing arm is made, at least partially, of steel, for instance of carbon steel, such as ST 34 and ST 52, light metal, aluminum, magnesium, titanium or an alloy thereof, or of a fibre-reinforced material. For example, a naturally hard alloy or a cold-ageing alloy can be used as alumium alloy.
It may be practical for reinforcing purposes if the hollow arm parts have, at least partially, moulded sections, such as longitudinal or transverse ribs. Thus, a further savings of material can be realized.
To improve the torsional rigidity of the arm, it is appropriate for the cross-sections of the projections and also those of the connecting parts in the connecting area to be assummetrical and/or angular, for example, triangular, quadrangular, polygonal or oval in shape. However, they can also be round.
The wall thickness can basically be constant across the entire, respective part of the swing arm.
It is practical if a connecting section is moulded at least at one end of the hollow swing arm in order to simplify the attachment of the swing arm, for example, to the side member of a motor vehicle.
Due to the IHM method, it is possible to produce particularly light parts of small dimensions, thus requiring a smaller structural space, as compared to hollow shells.
It is especially preferred if the swing arm, according to the invention, is basically made of ST 34 or ST 52 steel of a wall thickness of about 1 to 5 mm, preferably ranging between 1.5 and 2.5 mm.
The individual parts of the swing arm, fitted into one another, can be fastened to one another by way of welding, bonding, riveting, soldering and through other connecting techniques familiar to the expert.
For example, the projections on the individual parts can be cut open, thus creating an open part. However, it is also possible to use projections that have not been cut open, and just slip on the arm part. This will result in a slightly increased weight but will additionally reinforce the connecting area and, furthermore, it will save one operational step (to cut open). Depending on the realm of application, the expert can select relevant measures.
The swing arm can be, for example, a front swing arm or a rear swing arm for a motor-vehicle axle or for landing gears, such as an aircraft landing gear.
Due to the fact that a swing arm has now been provided, which consists of at least two parts and is produced from internal high-pressure moulded parts, such swing arm can be created more easily whilst maintaining the same or having even better load characteristics than the familiar parts composed of individual shells. Furthermore, a savings in materials, as compared to the familiar parts, can be achieved. In addition, the swing arm can be optimally adapted to the required structural space.
It is appropriate to cold-form such parts by way of the internal high-pressure moulding method. Cold deformation, according to the internal high-pressure moulding method, will result in strain-hardening, which provides the element with especially advantageous strength properties. In addition, cold-forming processes are energetically advantageous.
The internal high-pressure method as such is well known. By internal high-pressure method, also called the IHM method, is meant here the method which was described, for example, in Industrial Gazette No. 20 of Mar. 9, 1984, and also in xe2x80x9cMetal Deformation Techniquexe2x80x9d, Issue 1D/91, Page 15 and following pages: A. Ebbinghaus: Precision Workpieces of Light-Weight Construction produced through Internal High-Pressure Deformationxe2x80x9d, or also in xe2x80x9cMaterial and Operationxe2x80x9d, 123 to 243: A. Ebbinghaus: xe2x80x9cEconomic Construction with Precision Workpieces produced by way of Internal High-Pressure Deformationxe2x80x9d, and also in xe2x80x9cMaterial and Operationxe2x80x9d 122, (1991), 11 (1989) Pages 933 to 938. To avoid repetition, reference to the disclosure thereof is made hereinafter to the full extent. This method has been applied up to now to produce various moulded, hollow parts, for example, to produce built-up camshafts for attaching cams to a pipe, to produce hollow camshafts, space steering control shafts, but also motor vehicle frame components.
Owing to the internal high-pressure method, it is possible to produce hollow, metallic, structural elements, which are completely new, wherein the fibre flow of the walls runs basically parallel to the outer contour and where there is no buckling or other weakening. Due to the great wall strength resulting from the advantageous fibre flow, the hollow structural elements can, therefore, be constructed parallel to the outer contours, and strain hardening can be achieved in a lighter form than has been the case up to now, thus rendering a substantial savings in weight possible. It is also possible to use laminated materials for the mould, provided these can be deformed jointly. By selecting suitable materials, laminates can be lighter than solid materials, and have the additional advantage of absorbing vibration, or they can have other coatings on the the surfaces, according to the ambient stress (corrosion due to acids, etc.), so that such a part has, in addition, also advantageous damping characteristics which in the case at hand may be very desirable.
By having the material follow along the longitudinal axis of the pipe during the deformation, for example, by way of movable mould elements, it is possible to achieve a basically uniform wall thickness in the formed partxe2x80x94also when tip-stretching connecting elementsxe2x80x94so that a weakening of the wall thickness, due to the tip-stretching of projections, can be at least partially balanced and this can be achieved without weakening.
The swing arm, according to the invention, can be usedxe2x80x94naturally, with correspondingly adapted dimensions and possibly also materialsxe2x80x94in vehicles of any kind in order to ensure a flexible and vibration-damping suspension of single wheels.
It is possible that the material of the swing arm is multilayered, in which case the layers can be of the same or of variable material, which may be metallic or also non-metallic, plastic or ceramic. Depending on the material selected, an adaptation to respective realms of application is possible. For example, a metal part can be produced in a way in which it is corrosion resistant, or it can also be produced with xe2x80x9cmaterial-specificxe2x80x9d vibration damping.
It can be advantageous if the outer formed part has several mating layers running parallel to one another, which are made of the same or of different materials whose fibres run parallel to one another.
The entire structural part can basically consist of the same or of various light metals, especially for the purpose of weight savings. The light metal, for example, can be aluminum or an alloy therof, which could be corrosion resistant as an advantageous characteristic.
According to an advantageous method for producing hollow, moulded parts, a hollow, outer mould is produced in the customary manner by drawing, casting, extruding or by internal high-pressure moulding, which is subsequently finished by applying the familiar internal high-pressure method.
Depending on the demands made on the material, also multilayered metal pipes can be chosen as starting parts. Multilayered designs have the advantage that the surfaces of the hollow part are subjected to variable stress and that vibrations of any kind are more difficult to guide, which in turn decisively improves the vibration characteristic of the hollow part when used. The internal high-presure method makes it possible to produce already in one moulding process, projections, depressions, openings, etc. on the outer hollow part.
Variable hollow sections, such as rectangular sections, angular sections, pipes, etc. wherein the cross-sectional form can vary across the course of the part, can be used as arm parts.
Thus, a part is created which, compared to previous parts, weighs less and occupies less structural space, whilst the load capacity is the same or whilst the stressability is higher at a lower weight and which, in addition, can be manufactured at high production accuracy with a reduced scrap percentage rate.